Safety device for use on aircraft employing retractable landing gear



- 2' WHEELSDOWN Nov. 18, 1941. w, EX 0 2,262,756 SAFETY DEVICE FOR USE on AIRCRAFT EMPLOYING RETRACTABLE LANDING GEAR Filed Ma 8, 1940 AKE OFF MIXTURERICH SET PROP FUEL RESERVE COWL F LAPS SET TABS LOW BLOWER 38 FUELRESEPVE 1 FLAPS DOWN L 0 Q LANDING GEARS THRoTTL- cm-zcx on us'r CLOSED WITH WHEELS swrrcu CLOSED swn'cu CLOSED WHEN TURNED wnu THROTTLE To Nome cLosED INVENTOR UP 11E Z EDWARDWCLEXTON BY n ATTORN? Patented Nov. 18, 1941 SAFETY. DEVICE FOR USE ON Antone FT EMPLOYING A RETRACTABLE LANDING GEAR Edward w. Clexton, United States Navy Application May a, 1940, Serial No. 334,092 .j

Claims. (01. 177-311 (Granted under the act of March 3, 1883, as amended April so, 1928; 370 o. G. 757) This invention relates to a safety device for use on aircraft employing retractable landing gear, and has for an object to provide a circuit for actuating a warning device to warn the pilot that the retractable wheels are not extended only when the pilot is about to land, and'to prevent the Warning signal being falsely actuated at any other time, as for instance when the throttle is closed during formation flight, dive bombing, fighting, etc. i

With the present well-known system a warning device or howler is actuated by a switch which is closed when'the throttle is closed in a circuit operating through another switchwhich remains closedwhile the landing wheels are in retracted position. i 1 I With thepresent device it is the theory that when the pilot is about-to land he operates the landing gears to extend the wheels and closes the throttle as he a proaches his landing position; Should he fail to operate the landing gears, the closing of the throttle switch completesthe circuit to the howler, thereby reminding the pilot that he should operate his landing gears and thus disconnect the circuit to the howler.

In operation, however, especially in military planes, it is often necessary to close the throttle at many other times when it is not desired to land, as, for instance, in dive bombing, in formation flying, in fighting, or any other types of aerial acrobatics. With the present system, the howler or indicator is actuated each time the throttle is closed, so that after the pilot has been flying for some time he becomes so psychologically conditioned that he ignores the howler or warningindicator during such aerial acrobatics. However, ithas been found in actual practice that such habit of, ignoringthe howler or warning indicator when such warning is false, continues with the pilot so that he still ignores the howler or warning indicator when thewarning is true, and there have been thus manylandings attempted with the wheels in retracted position', thus damaging or wrecking the aircraft and injuring or killing the pilot. I

With this invention, howeveru e howler or warning indicator is operable only when the pilot is about to land the aircraft and is not operable during any previous aerial acrobatics, as a result of which, the pilot does not become falsely conditioned into a habit of ignoring the indicator,

but instead is conditioned into a habit of obeying the indicator which is actuated only when it should be obeyed.

.Advantage is taken of the fact that in each particular aircraft, certain particular steps must be taken when getting ready to take ofi or fly the aircraft, and anotherxseri'es of steps 'must be taken when getting ready to land the aircraft. To be sure that each necessary step is.

taken, it is desirable to provide a printed list visible to the pilot, showing what particular steps must be taken for the particular'aircraft when taking off, as well as when landing. With this invention, these particular steps are madeup into two lists, one a take-off list and the other. a landinglist, with only one list visible to "the pilot at all times. The pilot must take a posi-.

tive action to make the desired list visible to him. The act of selecting the desired list causes 3 this invention to become operative.

With the foregoing and other objects in View, the invention consists in the construction, combination and arrangement of parts hereinafter described and illustrated in the drawing, in which,

Fig. 1 isa diagrammatic outline of the circuit of the invention;

Fig. 2 is a front plan view of the check-off instrument used with this invention, showing the take-off list in visible position;

Fig. 3 is a view similar to Fig. 2, with the window and mask removed and the list plate in intermediate position as it is being turned from one side to the other;

Fig. 4 is a sectional view on line 4-4 of Fig. 33'" Fig. 5 is a side elevational view of the geared operating cylinder; and

Fig. 6 is a top elevational view of Fig. 5.

There is shown in Fig 1 the circuit I0 involving this invention. This circuit H1 includes a source of electrical energy as well as a battery ll, connected as at l2 by a conduit to a warningindicator or howler i3, which is grounded to the airplane framework as at M, the battery being grounded as at l5. 'llhisicircuit i0 is ordi narily provided with a throttle switch l6, which throttle switch I6 is normally open whenthe throttle is open and is closed by the act of closmg the throttle. Also provided in the circuit l0 1s a landing gear switch l1. This switch Il normally remains closed while the landing wheels are retracted iniiy'ing position, and is opened to interrupt the circuit by the act of actuating the landing gears to extend the wheels to landing position. U i

As thus far disclosed the circuit is conven tio'nal. It is obvious that the warning indicator or howler I3 is actuated'only while'the throttle is closed with the landing wheels in retracted landing wheels when he has closed the throttle preparatory to landing. However, with this type reason.

'side of the plate 2|.

I pilot what steps are to be taken preparatory to his of circuit the howler will be unnecessarily actuated if the throttle This invention provides a, third switch It in bore shoulder 32 of the fixed cylinder 3|. A stud switch; is closedfor any other 5 the circuit III. This third switch I8 is a checkoff list switch and is actuated in combination with and by a check-off list instrument-2|), which 1 i is shown in Figs. 2 to 6, inclusive. This check-- off list instrument 26 includes plate 2| having a take-off list .22 on one side. of

a check-on list the plate 2| and a landing list 23 on the other 2| is so connected to the switch l8 that the switch l8 is in circuit interrupting or open position when the take-01f list is visible to the pilot, and the switch 8 is in circuit completing position when the landing list 23 is visibleto the pilot. 1

When the pilot is about to take off he rotates the control knob 24 ina clockwise direction and makes the take-off listv22 visible to him, which simultaneously opens the switch 18 to circuit interrupting position. He then leaves the takeuntil, he is-ready to land, thus interrupting the circuit tov the howleror indicator |3, irrespective of the position of the throttle switch |6.' When aboutto land he rotates the control knob to make the landing list 23 visible to him through the instrumentwindow 26. This simultaneously actuatesthe switch l8 to circuit-completing position,'the landing list 23 thereby reminding the 3 landing. Should he then close his throttle and thus close his. throttle switch |6 before he has operated the landing" gears to extendhis landing wheels, the switch I1 being in closed position with the landing wheels in retracted position, 0

the circuit II) will be completed and the howler l3 will immediately operate to remind the pilot that hemust extend hislanding wheels.

The check-off instrument shows one con-j Thischeck-oif list plate 1 Ofi list :2 visible to him throughout the flight 25 24 counter-clockwise, as shown by the arrow 25,

o as the shaft ends venient way of connecting up the heck-off plate 2|to'the switch |8 in circuit l0; h v I As shown in Figs. 2 to 6, this check-off instrument 20 includes a housing 2! having a suitable opening. 28 through whichtheoconduit l-2 ex-- tends to the switch |8 mounted on a cross bar A 30," fixed in a'cylinder 3|, which cylinder 3| is sweated or otherwise secured immovably within the housing 21. This cylinder 3| is counterbored:

as at 32 and provides a trackway for rotatable rotatable sleeve 33 is a gear ring 34 which meshes with-a gear wheel 35 on a shaft 36, the control knob 24 being mounted on the shaft 36, whereby rotation of the control-knob 24, in one or, another correspondingly' rotates sleeve 33. Internally extending from the rear of; the sleeve 33 is an arm 36 having ajbent end 31 from whichextends a finger 38.

The switch |8 includesa. bifurcated tumbler. arm having a slot 4|so positioned, as shown; in Fig. 3,- that rotation'of the sleeve" 33 causes the flnger 38 to enter the slot 4| of the bifurcated arm40 and actuate the bifurcated tumbler arm 40 and open or close the switch '|8, depend- 1 ing upon its direction ofrotation; that is, the f 0 path of --the finger 39 is such that it enters the slot 4|,'itumbles it, and 'then'leaves thefslot 4| 1 as the sleeve 33 is rotated in either direction.

direction the gear 3 M sleeve 33. Secured to the forward end of the pin 43- may extend through the housing 21 and through the counterbored portion of the cylinder 3|, holding the sleeve 3| against accidental axial rotation and having a. guide pin 44 extending beyond the cylinder 3| into a quarter circumferential slot 45 in the sleeve 33 to permit rotation sleeve 33.

'A pair of half-moon shaped slots46 and 41 at the top and'bottom of sleeve 33 provide track-v ways for pivot shaft ends 48 extending through hubs 50 from the check-off plate 2|. The cylinder 3| is provided at its top and bottom with two parallel axiallytextending slots 5| into which the'pivot shaft ends 48 extend after passing through the half-moon shaped slots and 41. A headed'guidepin 52 fixed as at 53 in the sleeve 33 has a ball head 54 extended into slit 55 in'the check-off plate 2|.

. A mask 56 set into the edge of the housing 2'! spaced from the take-oh list 22 so as to provide a reflecting flange'for, any suit-,

is held slightly ably'mounted lighting bulb 5'! within the housing 21 to provide indirect lighting of the -.take-off-5 the window26 and a frame; 58 are secured to the edgeef thevhousing as,bysuitable screws6fl, the control shaft36 extending? list at night. Next which the pin 44 extends. Asthe sleeve rotates half-moon slots; means of the axially the pivot shaft ends 48 travel-in 46 and 47 and are causedby extending slots 5| in fixed cylinder 3| to move axially from the window 26 back into .the housand 21, reach their furthermost point and then forwardly again;v

48 reachlthe other ends of I ing,2| as the half-moon slots the half-moon slots 4631111 41., Meantime the head .54 of the headed pin. 52 moves within the.

2|, whereby the plate guide slot 55 of the plate 2| by rotation of knob 24 is caused to present either the take-off list22 or thelanding list '23 through the window. Simultaneously, as already described above, the, switch I8 is actuated to open position when the take-01f list 22 is visibleand to 23 is. visible, thusqplacing the circuit 12 in suitable condition only when the pilot getsreadyto land and has made the landing closedaposition when landing list for actuating the howler |3 list 23 visible, and not'otherwise.

Other modifications and changes in the number andarrangement of the what is hereinafter claimed.

The invention described herein may be manu factured and/or used by or for the Government of the United States of America forgovernmental purposes without'the payment of any royalties thereon or therefor.

I claim:

1. A safety device for use on aircraft employing retractable landing gear, comprising in corn?v bination "a check-off list means operable to a landing list position or a take-off list position, a, warning indicator, a source of electrical energy tosaid warning indicator, a.- circuit connecting said warning indicator to said source of electrical energy, a landing gear switch interrupting said of sleeve 33, but prevent axial movement of 3 a guiding V I v parts may be made by those skilled in the art without departing from i the nature of the invention, within the scope of switch interrupting said circuit circuit with the wheels in extended position, a throttle switch interrupting said circuit when the throttle is in closed position, and a manually op-' erable check-off list switch interrupting said circuit except when the check-off list means has been manually actuated to the landing list position.

2. A safety device. for use on aircraft employing retractable landing gear, comprising in combination a check-off list means operable to a landing list position or a take-off list position, a warning indicator, a source of electrical energy to said warning indicator, a circuit connecting said warning indicator to said source.of electrical energy, alanding gear circuit with the wheels in extended position, a throttle switch interrupting said circuit when the throttle is in closed position, a check-off list except when the check-off list means has been actuated to the landing list position, and manually operable means for selecting one 'of the check-off lists and simultaneously actuating the check-off list switch. I I

3. In a safety device for use on aircraft employing retractable landing gear and having a warning indicator, a source of electrical energy to said warning indicator, a circuit connecting said warning indicator to said source of electrical energy, a landing gear switch interrupting said circuit when the wheels are in extended position, a throttle switch interrupting said circuit when the throttle is in closed position, a checkofi list means manually operable to either a landing list position or a take-off list position, and a check-off list switch interrupting said circuit except when the check-off list means has been manually actuated to the landing list position.

4. In a safety device for use on aircraft employing retractable landing gear and having a circuit to a warning indicator including a throttle switch and a landing gear switch; a checkoff list switch means in the warning indicator circuit, said check-off list switch means com-- prising in combination a check-off list instrument, a check-off list plate rotatably mounted in said instrument, said check-oil list plate having a landing list on one face thereof and a takeswitch interrupting said off list on the opposite face thereof, a switch in said instrument,

and manually controllable means for rotating said check-oil list plate to either landing list exhibiting position or take-oi! list exhibiting position, said manually controllable -means including means to actuate said switch to circuit-interrupting position when said check-off list plate is moved to take-01f list exhibiting position, and to actuate said switch to circuit-completing position when said check-off list is moved to landing list position.

5. A combined check-off list indicating instrument and switch for the purpose disclosed comprising a check-oil list instrument, a check-off list plate rotatably mounted in said instrument, said check-off list plate having a landing list on one face thereof and a take-oi! list on the opposite face thereof, a switch in said instrument, and manually controllable means for rotating said check-off list plate to either landing list exhibiting pos tion or take-off list exhibiting position, said manually controllable means including means to actuate said switch to circuit-interrupting position when said check-off list plate is moved to take-oil list exhibiting position, to actuate said switch to and circuit-completing position when said check-off list is moved to landing list position, said manually controllable means comprising a cylinder within said instrument; a sleeve rotatably mounted in said cylinder, a pair of oppositely disposed axially extending slots in said cylinder, a pair of oppositely disposed half-moon shaped slots in said sleeve, 9.

shaft extending through said che'ck-ofi list plate and having its ends extending through said halfmoon shaped slots into said axially extending slits, a headed guidepin mounted in said sleeve, said check-offlist plate having a guide slot into which said guide pin extends, a switch operating arm extending from said sleeve, and manual means for rotating said sleeve within said cylinder to cause the check-off list plate shaft ends to travel in said slots and cooperate with" the headed guide pin to rotate said check-off list plate from one side to, the other and simultaneously actuate said switch.

EDWARD W. CLEX'I'ON. 

